1. Field of the Invention
The present invention relates generally to induction heating apparatus and more particularly to an exciter for an induction heating apparatus which may be applied for a heating element, such as a cooking pot. The exciter of this invention is quite effective for application to a commercial frequency excitation system. U.S. patent application Ser. No. 372,610 now U.S. Pat. No. 3,906,181 is another application of applicant's directed to induction heating apparatus.
2. Description of the Prior Art
It is known to use an induction heating apparatus for heating a heated element by applying an alternating magnetic field formed by AC current of 50 - 60 Hz of commercial frequency to a heated element, such as a cooking pot. Such use of induction heating type cooking apparatus is also known.
The exciters in such apparatus for generating the alternating magnetic field therein usually and conventionally comprise two or three disc iron cores having annular grooves therein and two or three ring windings which are coaxially fitted within these grooves. Such conventional exciters have the following disadvantages, namely that it is difficult to obtain high efficiency in theory alone, it is difficult to provide an alternative component of zero of the electromagnetic force applied to the cooking pot, to cause noise, and it is difficult to form the iron core.
Accordingly, an improvement of such exciters has been proposed having four equi-spaced magnetic poles connected to a yoke and windings wound on these magnetic poles, wherein the first excitation circuit is formed by connecting the windings wound on a pair of magnetic poles, which are not adjacent, on a diagonal line and the second excitation circuit is formed by connecting the windings wound on the other pair of magnetic poles and an excitation current having a phase difference of about 90.degree. is applied to the excitation circuits. In accordance with this exciter, the abovementioned disadvantages of the former exciters having coaxial ring windings can be overcome. However, this exciter has been found to possess such disadvantages as the cooking pot receiving a turning effect and the electromagnetic forces being applied to the cooking pot in a vertical direction not being balanced when the cooking pot is not placed at the center of the exciter, whereby the cooking pot is vibrated.